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51.
Julia Scharwächter Andreas Eckart Susanne Pfalzner Jens Zuther Melanie Krips Eva Schinnerer Johannes Staguhn 《Astrophysics and Space Science》2005,295(1-2):101-106
I Zw 1 and 3C 48 are two neighboring template objects at a later stage of the hypothesized merger-driven evolutionary sequence from ultra-luminous infrared galaxies (ULIRGs) to quasi-stellar objects (QSOs). Since galaxy mergers are assumed to trigger the evolution, it is important to confirm the merger properties of transitionary objects. Using multi-wavelength observations and N-body simulations, the merger histories of I Zw 1 and 3C 48 have been investigated in two separate case studies. Here, the results from both studies are compared and their relevance for the evolutionary hypothesis is discussed.This research is partly based on observations with ISAAC at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) under projects 67.B-0009 and 67.B-0019. 相似文献
52.
Julia Scharwächter Andreas Eckart Susanne Pfalzner Johannes Staguhn Eva Schinnerer 《Astrophysics and Space Science》2003,284(2):507-510
We address current theories of research on morphology, environment and evolution of active galaxies in the form of a detailed
case study of the nearby QSO host I Zw 1. This study is based on sub-kpc resolution 12CO(1-0) observations with the BIMA mm-interferometer and on near-infrared imaging with ISAAC at the VLT. The 12CO(1-0) maps reveal a circumnuclear molecular gas ring with a radius of 0.9 kpc. The imaging data in the J-band are analyzed
with respect to a disk-bulge decomposition. Together with a model of the gas rotation curve, the radial profile of the dynamical
J-band mass-to-light ratio (M/L) is discussed. The J-band images give new evidence for an interaction between I Zw 1 and its
nearby companion. First results from a sequence of N-body simulations for an extensive test of the parameter space of the
interaction are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
53.
54.
In this paper we study the evolution of a LRS Bianchi I Universe, filled with a bulk viscous cosmological fluid in the presence
of time varying constants “but” taking into account the effects of a c-variable into the curvature tensor. We find that the only physical models are those which “constants” G and c are growing functions on time t, while the cosmological constant Λ is a negative decreasing function. In such solutions the energy density obeys the ultrastiff
matter equation of state i.e. ω = 1. 相似文献
55.
Some Bianchi type I viscous fluid cosmological models with a variable cosmological constant are investigated in which the
expansion is considered only in two direction i.e. one of the Hubble parameter
is zero. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient
of shear viscosity is considered as constant in first case whereas in other case it is taken as proportional to scale of expansion
in the model. The cosmological constant Λ is found to be positive and is a decreasing function of time which is supported
by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed. 相似文献
56.
57.
志留系是塔里木盆地第一套砂岩储层广泛分布的沉积盖层,其沉积来源与成因对志留纪构造演化及周边造山带的研究具有重要意义。塔中地区3个志留系样品的碎屑锆石LA?ICP?MS U?Pb定年研究表明,志留系具有比较集中的二期物源年龄:南华纪中期、古元古代中期。碎屑锆石测定的年龄表明塔中志留系物源均来自前寒武纪,塔中东部源区方向的塔南隆起基底在奥陶纪已隆升成为蚀源区。大量的新元古代中期锆石年龄表明塔里木板块在新元古代时期可能与Rodinia超大陆具有相似的聚合与裂解演化史。 相似文献
58.
使用空间无关的公平性衡量指数评价公交服务时,会忽视公交服务需求与供给的空间分布特征。为解决此问题,论文提出基于空间公平理论的公交服务评价框架,即通过构建综合基尼系数与莫兰指数的空间公平评价方法,实现整体尺度公交服务评价;通过对分析单元上相对需求与相对供给变量的匹配关系、空间差距进行分析,实现局部尺度公交服务评价,对整体尺度结果进行补充。深圳市的案例研究表明:① 基于平等主义的整体尺度空间公平指数显示,空间公平性最好与最差的行政区均位于中心城区,分别为罗湖区与南山区;② 局部尺度分析结果进一步印证,单一使用基尼系数评价公交服务存在局限性,相同或接近的基尼系数可以对应完全不同的公交服务不公平状态与供需匹配情况。 相似文献
59.
Christopher Macdonald Hewitt 《The Cartographic journal》2017,54(2):106-114
Historical enclosure era property-related maps can tell us a great deal about the life and times of communities in the past. This study offers a unique approach to studying the historical landscape by applying GIS techniques to the examination of an eighteenth-century English village. Using novel GIS applications relying on historical maps, the study explores various aspects of the village’s physical and social characteristics. In doing so, the study forges effective linkages between cultural and landscape variables to reveal aspects of the historical landscape in eighteenth-century Britain previously inaccessible to researchers. This, in turn, provides a much more comprehensive and sophisticated template for future use by historical geographers in a number of contexts. 相似文献
60.
Discovering spatial and temporal patterns from taxi-based Floating Car Data: a case study from Nanjing 总被引:1,自引:0,他引:1
Floating Car Data (FCD) refers to the trajectories of vehicles equipped with Global Positioning System-enabled devices that automatically record location-related data within a short time interval. As taxies in Chinese cities continually drive along the streets seeking passengers, FCD can easily traverse the entire street network in a city on a daily basis. Taking advantage of this situation, this study extracted passenger pickup and drop-off locations from FCD sourced from 6445 taxis over a 2-week period in Nanjing, China to discover human behavioral patterns and the dynamics behind them. In this study, road nodes are converted to the points, based on which Thiessen polygons are generated to divide the study area into small areas with the goal of exploring the spatial distribution of pickup and drop-off locations. Moran’s I index is used to calculate the spatial autocorrelation of the spatial distribution of pickup and drop-off locations, and hot spot analysis is used to identify statistically significant spatial clusters of hot and cold spots. The spatial and temporal patterns of FCD in the study area are investigated, and the results show that: (1) the temporal patterns show a strong daily rhythm, (2) the spatial patterns show that the number of pickup and drop-off locations gradually diminish from the downtown areas to the outer suburbs, (3) the spatiotemporal patterns exhibit large differences over time, and (4) the driving forces explored by regression models indicate that population density and transportation density are consistent with the population distribution, but per capita disposable income is not consistent with the population distribution. 相似文献